The present invention relates to a method for fabricating a semiconductor device, more specifically a method for fabricating a semiconductor device in which ferroelectric film is formed by metal organic chemical vapor deposition.
Recently, it is noted to use ferroelectric materials as the dielectric film of capacitors. The FeRAM (Ferroelectric Random Access Memory) using such ferroelectric capacitors is a nonvolatile memory having characteristics of being operative at high speed, small electric power consumption, good write/read durability, etc. and is very prospective.
As materials of such ferroelectric film, ferroelectric materials having the layered perovskite structure, PZT (lead zirconate titanate), etc. are noted. To form such ferroelectric films, MOCVD (Metal Organic Chemical Vapor Deposition), which can deposit ferroelectric film on large-area substrates with good step coverage and at high rates, is noted.
When a ferroelectric film is formed by MOCVD, concavities and convexities are formed in the surface thereof due to its crystal structure, etc., which often causes the problem of rough surface morphology. When concavities and convexities are formed in the ferroelectric film surface, the concavities and convexities are formed also in the surface of a conducting film formed on the ferroelectric film. When a resist is applied to such conducting film, and light is applied to expose the resist, the incident light is diffused by the concavities and convexities in the conducting film surface, which makes it difficult to form patterns with good accuracy.
As countermeasures, the cavities in the ferroelectric film surface are filled with an insulation film to thereby improve the surface morphology (Patent Reference 1 and Patent Reference 2). The Patent Reference 1 is Specification of Japanese Patent Application Unexamined Publication No. 06-032613. The Patent Reference 2 is Specification of Japanese Patent Application Unexamined Publication No. 2003-282560. Patent Reference 3 is Specification of Japanese Patent Application Unexamined Publication No. 2002-170938.
However, filling the cavities in the ferroelectric film surface cannot sufficiently improve the surface morphology and furthermore, the insulation film buried in the ferroelectric film surface is left with a resultant problem that the characteristics of the ferroelectric capacitors are deteriorated.